ALAMEDA -- There was no sign of receiver Darrius Heyward-Bey (concussionneck strain) on the field during the media window of practice Thursday morning, nor were cornerback Shawntae Spencer (right foot) or right tackle Khalif Barnes (groin) seen.Defensive tackle Richard Seymour (knee), though, was practicing a day after taking the day off.Also, tight end Brandon Myers (concussion) was practicing for the second straight day, though it is unknown how far along he is in the concussion protocol that would clear him to play Sunday in Denver.Newly signed defensive end Andre Carter was practicing and wearing No. 97.Earlier, the Raiders announced they had signed linebacker Carl Ihenacho to the practice squad and released defensive back Akwasi Owusu-Ansah from the practice squad. Ihenacho initially made the 53-man roster out of training camp but was waived Tuesday to make room for linebacker Vic So'oto.